Inquiring about calibrating an analog machine with a test CD, inSync reader Sean C. asks: “I recently acquired an analog 8-track and I am wondering how a ‘test CD’ played through a commercial CD player compares to a traditional sine wave generator. Is the output of my commercial CD player good enough, as long as I observe input versus output on my 8-track?”
Thanks for the inquiry. Most “reference” CD’s I’ve seen are no match for the flexibility and quality of a “good” signal generator, but for all practical purposes you should be fine. The differences are subtle and should not be an issue calibrating your analog machine. The only real concern is the quality of the CD. Did they record a “true” sine wave or some stepped approximation? Is it recorded at a known reference level or just some arbitrary level? Even if the answers to those questions are unknown you can probably still get by with it as long as you are careful with levels in and out of the tape machine. Calibrate with the CD and see how good a recording your machine makes. It will probably be fine.